The present invention relates to internal combustion engines, and particularly to the piston-type internal combustion engine including a cylinder and a piston movable therein through induction, compression, expansion and exhaust strokes.
Commonly used today in automobiles is the conventional four-stroke Otto-cycle engine, the engine output usually being varied by means of a throttle which controls the amount of fuel mixture inducted into the engine. One drawback of such an engine is that the Otto-cycle, in which the induction and compression strokes are equal to the expansion and exhaust strokes, does not enable as complete combustion and exhaust of the combustion gases, as, for example, the Atkinson-cycle engine. The latter uses longer strokes for expansion and exhaust than for induction and compression, and thereby obtains more complete expansion and exhaust. The Otto-cycle engine is therefore not as efficient as the Atkinson-cycle engine. Another disadvantage of the conventional Otto-cycle engine is that the throttle, when partially or completely closed to lower the engine output, causes pumping losses and thereby further reduces engine efficiency. A further disadvantage is that the incomplete combustion of the fuel causes serious air-pollution problems.